Flow control device including a pressure-balanced single-seated valve plug

ABSTRACT

A flow control device providing for large flow capacity together with tight shutoff by the use of large pressure balanced singleseated valve plug having passage means therethrough, with a separate single-seated valve plug for opening and closing the passage means, the large valve plug being opened and closed with a minimal force output actuator.

plug for X 13 O1 3 0 m3 76 3 7 3 1 g for large flow [56] ReferencesCited UNITED STATES PATENTS 938,491 11/1909 1,031,294 7/1912 Schutte...1,797,054 3/1931 Doran 1,877,542 9/1932 Wagner... 2,561,214 7/1951Matson.......................

Primary Examiner-Clarence R. Gordon Attorney-Molinare, Allegretti,Newitt & Witcoff ABSTRACT: A flow control device providin capacitytogether with tight shutoff by the use of large pressure balancedsingle-seated valve plug having passage means therethrough, with aseparate single-seated valve opening and closing the passage means, thelarge valve plug being opened and closed with a minimal force outputactuator.

Victor E. Skov; Richard F. Lytle, Marshalltown, Iowa Appl. No. 768,852Filed Oct. 18, 1968 [45] Patented May 25, 1971 Fisher Governor CompanyFLOW CONTROL DEVICE INCLUDING A PRESSURE-BALANCED SINGLE-SEATED VALVEPLUG 5 Claims, 1 Drawing Fig.

[52] 137/630.15 Int. Fl6k 11/22 137/629, 630, 630.15, 630.18, 630.21

United States Patent [72] Inventors CharlesB.Schuder;

[73] Assignee [50]FieldoiSearch............................................

.mi .M... w \\\\\\A\\\ i I g FLOW CONTROL DEVICE INCLUDING A PRESSURE-BALANCED SINGLE-SEATED VALVE PLUG BACKGROUND OF THE INVENTION Thisinvention relates to a flow control device and, more particularly, to aflow control device for accommodating large flow capacity together withpositive shutoff through utilization of a balanced valve plug capable ofbeing throttled from closed to open and back to closed with a minimalforce output actuator.

The design problems of tight shutoff and large flow capacity aresometimes at odds with one another. For example, where tight shutoff isof primary concern, single-ported valves are usually considered. As thepressure and/or the port size increases, large-size actuators arenecessary for moving the valve and the size of the actuator oftenbecomes the limiting factor in valve application. Under this designapproach, many applications require several valves in parallel to do therequisite control job.

In the event that a large flow capacity is the prime consideration,then, double-ported valves are usually considered and because of theirsemibalanced nature, they can usually be handled with reasonably sizedactuators. However, as the pressure drop increases, instability canbecome a problem and again a larger actuator is required. Where positiveshutoff, in addition to large flow capacity, is required, this approachis usually not successful.

An object of the present invention is to provide an improved flowcontrol device of large flow capacity having a balanced valve plugcapable of being throttled from closed to open and back to closed with aminimal output actuator, such valve plug having positive shutoff whenseated.

Another object of the present invention is to provide an improved largecapacity flow control device having tight shutoff, such device utilizinga large pressure-balanced single-seated valve plug and a separatesingle-seated valve plug, the two valve plugs being selectively actuatedby suitable actuating means, with the first valve plug controlling flowthrough the flow passage in the device and the second valve controllingflow through passage means in the first valve plug.

Yet another object of the present invention is to provide an improvedflow control device having a cup-shaped main valve plug therein forcontrolling flow through the main flow passage in the valve body, withpassage means in the main valve plug for registering pressure from theflow passage to a chamber above the piston remote from the flow passage,and with a separate single-seated valve plug for opening and closing thepassage means, the valve plug for opening and closing the passage meansthrough the main valve plug being operable to be opened before the mainvalve plug is opened to equalize pressure in the chamber above the valveplug with the pressure in the flow passage. Other objects and advantagesof the present invention will be made more apparent hereinafter.

BRIEF DESCRIPTION OF THE DRAWING There is shown in the single FIGURE ofdrawing attached a cross-sectional view of a flow control deviceembodying the present invention.

DETAILED DESCRIPTION OFTHE PRESENT INVENTION Referring now to the FIGURE'of the drawing, there is shown a large flow capacity flow controldevice 10 which provides' positive shutoff when he main or first valveplug and the second or secondary valve plug therein are seated. The flowcontrol device-10 includes a main valve body 12 having an inlet 13 andan outlet 14 communicated by a flow passage 16 within the valve body 12.The flanges at the ends of the main valve body 12 are adapted to aid inthe connection of the valve body in a pipeline; The housing means forthe flow control device I0 includes not only the main valve body I2,but, also, the upper bonnet l8 and the lower bonnet 20. The bonncts l8and 20are suitably connected to the valve body by fastening means, forexample, nuts 22 secured to studs 24V Disposed within the housing FIGUREof flow control device 10 is a tubular valve plug cage 26. The cage 26is retained between the upper bonnet l8 and a shouldering apertured wall28 of the main valve body I2. Sealing gasket 27 is between bonnet l8 andthe upper end of cage 26 and sealing gasket 29 is disposed between thecage 26 and a wall 28.

Movable axially within the valve cage 26 is the main valve plug 32. Themain valve plug 32 takes the form of an inverted cup-shaped memberhaving a central or post portion 34 extending downwardly therefrom. Thelower end of the cup shaped portion of main valve plug 32 is adapted tocooperate with a main valve seat 36, which in the illustrated embodimentof the invention, is defined by the lower end of the cage 26, but, whichcould be a separate element.

The cage 26 has flow openings 38 in the lower half thereof as well as anopening 40 defined through the lower end thereof. The upper half of thecage 26 acts as a cylinder for the valve plug 32. A piston ring 42 isprovided about the main valve plug 32 and acts between the valve plug 32and the inner wall of the cage 26 to restrict the'annular flow pathbetween the valve plug 32 and cage 26 to keep the clearance flow ofinlet pressure to the top side of the valve plug 32 to a minimum.

The valve plug 32 is suitably affixed to a main valve plug stem 50 thatis, in turn, connected to main actuator indicated schematically at 52.The yoke 54 of the actuator is adapted to be connected to the upperbonnet 18 by suitable fastening meansv Packing means 56 are providedabout the main valve plug stem 50 to seal between the valve plug stem 50and the upper bonnet 18.

There are provided within the main valve plug 32 passage means 61 forcommunicating the chamber 60 with pressure in the flow passage 16. Thechamber 60 is remote from flow passage 16 and is defined by the top ofthe main valve plug 32, the walls of the cage 26 and the lower portionof the bonnet l8. Passage means 61 include openings 62 in the top of thecup-shaped portion of the valve plug 32 and registration openings 64 inthe hub portion 34 of the main valve plug 32. Openings 62 and 64 areconnected by an axial opening 66 in the hub portion 34 which receives asecondary valve plug 68. The secondary valve plug 68 is adapted to abutagainst a shoulder or seat 69 defined in the main valve plug between theopenings 62 and 64. The secondary valve plug 68 is suitably connected toa secondary valve plug stem 72 for actuation axially toward and awayfrom seat 69. The valve plug steam 72 is connected with a secondaryactuator indicated generally at 74. The actuator 74 includes a yoke 76suitably affixed to the lower bonnet 20, as, for example, by locknut 78.Packing means 80 are provided about the valve plug stem 72 to sealbetween the valve plug stem 72 and the lower bonnet 20.

Normal flow of fluid through the main valve body 12 is through the inletopening 13, the openings 38 in cage 26 beneath the main valve plug 32,through the main port or opening 40 in the valve seat portion 36 of thecage 26 and out the outlet 14. During flow or anytime that the secondaryvalve plug 68 is traveled open by the actuator 74, the pressure abovethe main valve plug 32 in chamber 60 and the pressure under the mainvalve plug 32 are equalized through the passage means 61 in the mainvalve plug, resulting in minimum actuator force requirements.

It will be noted that the registration openings 64 in the main valveplug are angled downwardly and outwardly, so as to sense accurately thepressure in the recessed area 33 below the inverted cup-shaped mainvalve plug 32. The pressure detected by the registration openings 64must be representative of the average static pressure below the mainvalve plug. It was found that if a cup-shaped valve plug 32 wereutilized which did not include the central hub portion, such that thesecondary valve plug 68 acted directly against the valve seat 69 andpressure was sensed only axially of the main valve plug 32 that animproper pressure was registered against the top of the main valve plug.By fabricating the main vale plug 32 with a recessed area 33 and withoutwardly disposed registration openings 64 in the hub portion 34, asshown, an average static pressure below the main valve plug can beregistered in the chamber 60 above the main valve plug. The key tosensing an average static pressure is to locate the registration openinginlets away from the central portion of the hub 34.

During the period of shutoff, the secondary valve plug or actuator 68closes off the pressure balance registration holes 64 in the main valveplug 32. With the main valve plug 32 on the seat 36 and the registrationholes or openings 64 closed by secondary plug 68, the main valve plug 32will be positively closed. Further, with the flow in the flow-downdirection, the force developed on top of the main valve plug 32 inchamber 60 aids in a more positive closure of the main valve plug 32against seat 36, as well as increasing the loading on the gasket 29between the valve cage 26 and the wall 28 of main valve body 12.

The flow through the registration holes 64 when the main valve plug 32is seated is inthe flow-open direction for the secondary valve plug 68.The opening or hole defined in the valve seat 69 for closure by thesecondary valve plug 68 is relatively small and can easily be handled bya relatively small secondary actuator 74.

In operation, the secondary valve plug 68 is opened first to "equalizethe pressure on top of the main valve plug 32 with that below the valveplug 32. This will allow the mainactuator 52 to open main valve plug 32.The travel of the valve plug 68 is short, allowing guiding of the valveplug 68 within the bottom end of the hub portion 34 of the main valveplug 32 and keeping the pressure registration through main valve plug 32at the proper position. The main valve plug 32 must close first beforethe secondary valve plug 68 can be actuated closed for final shutoff.The actuating means which include separate actuators S2. and 74 foroperating the valve plugs 32 and 68, respectively, are interlocked forselective actuation of the valve plugs. The actuators may bepneumatically or mechanically interlocked, as desired.

Vent openings 59 in the wall of cage 26 permit condensate to escape fromchamber 60 when the flow control device is used in steam applications.Openings 59 are locatedjust above the top of the main or first valveplug 32 when the valve plug is seated against its seat 36.

The central hub portion 34, which may be formed unitarily with thecup-shaped portion or from a separate piece secured to the cup-shapedportion, may be provided with four registration holes 64 and the top ofthe cup-shaped portion of the main valve plug may be provided with twooutlet openings 62.

The specific number of openings is not critical provided that therelationship of the area of the openings 64 with respect to the area ofthe clearance between cage 26 and plug 32 is maintained. The passagearea through the main valve plug must be large enough to preventpressure buildup in chamber 60 greater than that in the recess 33 belowthe main valve plug. A rule of thumb is that the area of the clearancebe one-seventh the cross-sectional area of the passage means. The pistonring 42 aids in minimizing the crosssectional area required in thepassage means 61.

There has been provided by the present invention a flow control devicecapable of handling large flow capacity with tight shutoff. Providedwithin the housing means of the flow control device are twosingle-seated valve plugs which are actuated by interlocked actuatormeans, the first valve plug con trolling the flow of fluid through theflow passage in the valve body and the second valve plug controllingpressurization of g the side of the first valve plug remote from theflow passage.

to form a chamber remote from the flow assage, passage means in thevalve plug communicating the ow passage with the chamber, a second valveplug for opening and closing the passage means, and actuating means forselectively actuating the valve plugs and the second valve plug beingopened before the first valve plug to equalize pressure in the chamberwith pressure in the flow passage, the first valve plug being generallyin the form of an inverted cup having a depending central hub portion,the passage means including an opening in the top of the cup andoutwardly disposed registration opening in the hub portion, with asecondary valve seat defined between said opening in the top of the cupand said registration opening, said second valve plug being movableaxially within said hub portion toward and away from engagement withsaid secondary valve seat, and a tubular valve cage disposed in thevalve body, the first valve plug being movable axially in the valvecage, and said valve cage having opening means in the wall thereof,there being vent openings in the wall of the valve cage disposed abovethe top of the first valve plug when the first valve plug is seatedagainst the main valve seat.

2. A flow control device as in claim 1 wherein the actuating means isoperative to close the first valve plug before the second valve plug isclosed.

3. A flow control device as in claim 1 wherein the actuating meansincludes a first actuator for the first valve plug and a second actuatorfor the second valve plug.

4. A flow control device as in claim 1 wherein the area of theregistration opening is relatively small with respect to the area of theflow opening through the valve seat, the registration opening beingdisposed so as to sense the average static pressure in the space betweenthe cup and the central hub portion.

5. A flow control device as in claim 1 wherein the area of clearancebetween the valve cage and the first valve plug is on the order ofone-seventh of the cross-sectional area of said passage meansv

1. In a flow control device, a valve body having an inlet and an outletcommunicated by a flow passage with a main valve seat therein, a firstvalve plug movable to open and close the flow passage, said valve plugcooperating with the valve body to form a chamber remote from the flowpassage, passage means in the valve plug communicating the flow passagewith the chamber, a second valve plug for opening and closing thepassage means, and actuating means for selectively actuating the valveplugs and the second valve plug being opened before the first valve plugto equalize pressure in the chamber with pressure in the flow passage,the first valve plug being generally in the form of an inverted cuphaving a depending central hub portion, the passage means including anopening in the top of the cup and outwardly disposed registrationopening in the hub portion, with a secondary valve seat defined betweensaid opening in the top of the cup and said registration opening, saidsecond valve plug being movable axially within said hub portion towardand away from engagement with said secondary valve seat, and a tubularvalve cage disposed in the valve body, the first valve plug beingmovable axially in the valve cage, and said valve cage having openingmeans in the wall thereof, there being vent openings in the wall of thevalve cage disposed above the top of the first valve plug when the firstvalve plug is seated against the main valve seat.
 2. A flow controldevice as in claim 1 wherein the actuating means is operative to closethe first valve plug before the second valve plug is closed.
 3. A flowcontrol device as in claim 1 wherein the actuating means includes afirst actuator for the first valve plug and a second actuator for thesecond valve plug.
 4. A flow control device as in claim 1 wherein thearea of the registration opening is relatively small with respect to thearea of the flow opening through the valve seat, the registrationopening being disposed so as to sense the average static pressure in thespace between the cup and the central hub portion.
 5. A flow controldevice as in claim 1 wherein the area of clearance between the valvecage and the first valve plug is on the order of one-seventh of thecross-sectional area of said passage means.